← IGCSE Computer Science Paper 1

Following one digital currency transaction through the blockchain

The order a payment follows: the sender makes it, it is time-stamped, placed in a block, and the block joins the chain, so the record becomes permanent.

Part of: IGCSE Computer Science 0478 — 5.2 Digital Currency — Module 22

Understanding Following one digital currency transaction through the blockchain in IGCSE Computer Science Paper 1

What it does: Time-stamped transactions are placed in a block. A block holds a group of transactions. When the block joins the chain, the transaction record cannot be altered, so it is permanent. The time-stamp records when the payment was made, which keeps transactions in order. It does not give the sender a way to cancel.

Common mistakes: The payment must be time-stamped with the current time, so the line should be payment.time ← NOW(). Erasing the time would leave no record of when it happened. A payment is placed in a block first. The chain is built from blocks, not single payments, so the line should be block.ADD(payment).

Class: _____________________ · Name: _____________________ · Date: _________

Free printable worksheet with full answer key — or add this module to a class and your students practise it interactively.

🖨 Print worksheet + answer key Add Following one digital currency transaction through the blockchain to a class →

This module's key terms are also in a printable crossword (Modules 510–519) and word search (Modules 510–546).

Take this worksheet further — free with Cloodit

Each concept is reinforced from every angle — learned, then applied, then tested.

Learning

Duo

Which step happens FIRST when a digital currency payment is sent?

The sender makes the payment (the transaction)The block joins the chain

Matches

payment -> block -> time-stamp -> chain

↓

The time-stamp is added too late. The transaction must be time-stamped before it is placed in a block.

Applying

Meanings

Term

transaction -> time-stamp -> block -> chain

Meaning

The order a payment follows: the sender makes it, it is time-stamped, placed in a block, and the block joins the chain, so the record becomes permanent.

Practice

transaction ← MakePayment(sender, receiver, 5)

Testing

Gaps

Step 2: payment is

Check Answer

Spots

2payment ← MAKE(sender, 20)

3payment.time ← ERASE()

Cloodit turns curriculum-aligned coding content into journeys students work through one biome at a time.

Students earn collectable badges

Over 100 of them, across seven natural biomes.

Study Buddy

Students build a real study resource

Turns their work into revision material ready for Flash Cards and Exam study.

Diamond Dash — one of Cloodit's live, competitive Sprint games

Students lock in with Sprints

Live, competitive practice for the start of the lesson or a teacher-led lesson finisher.

A Cloodit certificate of achievement, ready to personalise and print

Custom printable certificates

Honour your top performers, or encourage a student who's trying hard — ready to print in seconds.

Add to class →

Quick Questions

1. Which step happens FIRST when a digital currency payment is sent?

A. The block joins the chain

B. The sender makes the payment (the transaction) ✓

Everything starts with the sender making a transaction. The block can only join the chain after the transaction has been made, time-stamped and placed in a block.

2. What happens to a transaction straight after it is made?

A. It is time-stamped with the date and time ✓

B. It is deleted from the network

The transaction gets a time-stamp showing when it happened. It is not deleted, because the record needs to be kept.

3. Which is the correct order for one transaction?

A. Block, chain, transaction, time-stamp

B. Transaction, time-stamp, block, chain ✓

The payment is made, then time-stamped, then placed in a block, and finally the block joins the chain. A block cannot exist before there is a transaction to put in it.

4. Where is a time-stamped transaction placed before it becomes part of the chain?

A. In a block with other transactions ✓

B. In the sender's digital wallet only

Transactions are grouped into a block. The block is then added to the blockchain. The wallet only holds the currency, not the permanent record.

5. What happens once a block is full of time-stamped transactions?

A. The block is added to the end of the chain ✓

B. The block is sent back to the sender to be changed

The finished block joins the chain, after the previous block. It is not sent back, because blocks cannot be altered.

Match the Pairs

sender -> payment → The first step: the sender makes a payment, which creates a new transaction

payment -> time-stamp → The transaction is given the exact date and time it was made, so its place in the order is fixed

The time-stamped transaction is stored together with other transactions in a group → transaction -> block

Once the block is joined to the end of the blockchain, the record is permanent → block -> chain -> permanent

payment -> block -> time-stamp -> chain → The time-stamp is added too late. The transaction must be time-stamped before it is placed in a block.

payment -> time-stamp -> chain -> block → The steps at the end are the wrong way round. The transaction goes into a block first, and then the block joins the chain.

Key Term

transaction -> time-stamp -> block -> chain

The order a payment follows: the sender makes it, it is time-stamped, placed in a block, and the block joins the chain, so the record becomes permanent.

Fill in the Blanks

1. Step 1: sender makes a payment Step 2: payment is time-stamped Step 3: payment is put in a block

Hint: Type the word for recording the exact date and time of the payment

2. Step 1: sender makes a transaction Step 2: transaction is time-stamped Step 3: transaction is placed in a block

Hint: Type the name of the group that holds several transactions

3. Step 3: transaction is placed in a block Step 4: the block joins the chain Step 5: the record is permanent

Hint: Type the name of the linked structure that blocks are added to

4. The sender makes the payment The payment is time-stamped The payment is placed in a block

Hint: Type the role of the person who starts the transaction

5. Step 4: the block joins the chain Step 5: the record is now permanent

Hint: Type the word that describes a record that can no longer be changed

Spot the Error

Question 1

A sender ← 'Ava'

B payment ← MAKE(sender, 20)

C payment.time ← ERASE()

D block.ADD(payment)

Line C — The payment must be time-stamped with the current time, so the line should be payment.time ← NOW(). Erasing the time would leave no record of when it happened.

Question 2

A payment ← MAKE('Ava', 20)

B payment.time ← NOW()

C chain.ADD(payment)

D chain.ADD(block)

Line C — A payment is placed in a block first. The chain is built from blocks, not single payments, so the line should be block.ADD(payment).

Question 3

A payment ← MAKE('Ben', 15)

B payment.amount ← NOW()

C block.ADD(payment)

Line B — The time-stamp belongs in the time field. It must not overwrite the amount, so the line should be payment.time ← NOW().

Question 4

A IF payment.time ≠ NULL THEN

B block.ADD(payment)

C chain.REMOVE(block)

D ENDIF

Line C — Once a payment is in a block, the block joins the chain. It is not removed from it. The line should be chain.ADD(block).

Question 5

A payment ← DELETE('Dee', 30)

B payment.time ← NOW()

C block.ADD(payment)

Line A — A transaction starts when the sender makes a payment, so the line should use MAKE. A deleted payment can never be time-stamped or added to a block.

Student with a class code? Join your class →